Process of preparing a silica-alumina supported group viii metal hydrocracking catalyst



United States Patent ()fifice 3,274,124 Patented Sept. 20, 19663,274,124 PROCESS OF PREPARING A SILICA-ALUMINA SUPPORTED GRUUP VillliMETAL HYDRO- CRACKING CATALYST Mark J. OHara, Mount Prospect, 111.,assignor to Universal Oil Products (lompany, Des Plaines, 111., acorporation of Delaware No Drawing. Filed Jan. 2, i964, Ser. No. 335,3496 Claims. (Cl. 252451) This application is a continuation-in-part of mycopending application, Serial No. 145,758, filed October 17, 1961, nowabandoned, which in turn is a continuation-inpart ofmy application,Serial No. 14,525, filed March 14, 1960, now abandoned.

This invention relates to a process for the catalytic cracking ofpetroleum hydrocarbons in the presence of hydrogen. More particularly,it relates to the hydrocracking of relatively high boiling petroleumhydrocarbons in the presence of a novel hydrocracking catalyst toproduce petroleum hydrocarbons boiling within the gasoline range.

The various catalytic cracking processes, wherein relativelyhigh-boiling petroleum fractions are subjected to pyrolysis in thepresence of acidic catalysts to form more desirable petroleum fractionssubstantially Within the gasoline boiling range, have found wideacceptance in the field of petroleum refining. While the art ofcatalytic cracking has progressed to a high degree of perfection sinceits inception, it nevertheless retains certain characteristics whichdeter from its overall efiiciency. For exam ple, carbon deposition onthe catalyst, while desirable to a certain extent in the fluidized typeof process for heating purposes, amounts on the average to about 7%. Itis generally considered that a carbon content of about 3% Would servethe requirements of the fluidized process,

while of course a fixed bed type of process would be better served bythe elimination of substantially all of the carbon deposition.

Furthermore, in addition to the gasoline boiling range products, a cyclestock is recovered which is further separated into a light cycle oil anda heavy cycle oil. The

heavy cycle oils are generally recycled for cooling purposes beingrefractory in nature. The light cycle oil must be disposed of asinferior distillate fuel oil or it must be thermally cracked sincerecycling to extinction in a cataresult the availability of suitablecracking stocks has been somewhat restricted. Gasoline yields arefurther reduced by the formation of C -C gaseous products which accountsin some cases for about 10% of the charge stock.

When the high boiling petroleum hydrocarbon fractions are subjected tocracking conditions in the presence of hydrogen and a suitable cataylstthe foregoing limitations on the catalytic cracking process are largelyeliminated. While the beneficial features of the hydrocracking processhave long been recognized, their application has been hindered by thelack of a suitable catalyst. The catalysts employed must necessarilyembody hydrogenation as well as cracking characteristics.

It is an object of the present invention to provide an improved processfor the catalytic cracking of heavy petroleum charge stocks in thepresence of hydrogen.

More specifically, the object is to present a process for the catalytichydrocracking of heavy petroleum fractions in the presence ofhydrogenation catalyst deposited on a particular synthetic composite,said composite embodying characteristics which contribute to a highdegree of conversion of heavy petroleum hydrocarbon fractions togasoline boiling range petroleum fractions and/or high quality fueloils.

By the phrase gasoline boiling range petroleum fractions it is intendedto refer to those petroleum fractions comprising volatile hydrocarbonswhich. boil substantially continuously in the range of from about 60 F.to about 410 F.

Other objects and advantages of this invention will become apparent inthe following detailed specifications.

In one of its broadest aspects this invention embodies a process for thecatalytic hydrocracking of a petroleum hydrocarbon which comprisescracking said petroleum hydrocarbon in admixture with hydrogen athydrocracking conditions in the presence of a catalyst comprising ametal of Group VIII deposited on a synthetic composite of silica andalumina, said silica-alumina composite having been prepared bycommingling an alkali metal silicate solution with a suflicient quantityof a mineral acid solution to form an acidic salt-containingsilica sol,first gelling and aging the resultant salt-containing sol under acidconditions and then adding analkaline reagent and further aging theresultant gel under basic conditions, commingling the resultant aged gelwith an aluminum salt solution, precipitating a silica-alumina compositetherefrom by the addition of a basic precipitant; water-washing thefreshly precipitated and undried silica-alumina composite sufficientlyto remove from about 10% to about but not all of the water soluble saltstherefrom, drying said water-washed silica-alumina composite at atemperature of from about 200 F. to about 500 F., and furtherwater-washing the resultant dried silica-alumina to remove the remainingwater soluble salts therefrom prior to a final calcination thereof.

A more specific embodiment is in a process for the catalytichydrocracking of a petroleum hydrocarbon boiling in the range of fromabout 400 F. to about 1200 E, which comprises cracking said pe-troieumhydrocarbon resultant salt-containing sol at a pH of from about 4 toabout 4.5, and then adding an alkaline reagent and further aging theresultant gel at a pH of from about 7 to about 7.5, commingling theresultant aged gel with an aluminum salt solution, precipitating asilica-alumina composite therefrom by adding a sufiicient amount of abasic precipitant to raise the pH to about 8, water-washing saidsilica-alumina composite sufficiently to remove from about 30% to about60% but not all of the Water soluble salts therefrom, forming an aqueousslurry of said Water-washed silica-alumina composite and spraying theslurry in an atomized state into an atmosphere of hot inert gasesmaintained at a temperature of from about 200 F. to about 500 F. toeffect a rapid evaporation of the moisture therefrom, and furtherwater-washing the resultant spray dried silica-alumina t c-remove theremaining Water soluble salts therefrom prior to a final calcinationthereof at a temperature of from about 800 F. to about 1400 F.

In accordance with the process of this invention a petroleum hydrocarbonfraction boiling in the range of from about 400 F. to about 1200 F. iscatalytically cracked in the presence of hydrogen at a pressure of fromabout 500 p.s.i. to about 3000 p.s.i. and at a temperature of from about400 F. to about 1000 F.

Petroleum hydrocarbon fractions which can be utilized as charge stocksaccording to the process of this invention thus include the gas oils,fuel oils, kerosenes, etc., recovered as distillate in the atmospheredistillation of crude oils, also the light and heavy vacuum gas oilsresulting from the vacuum distillation of the reduced crude, also thelight and heavy cycle oils recovered from the catalytic crackingprocess, light and heavy coker gas oils resulting from low pressurecoking, also coal tar distillates and the like. Residual oils, oftenreferred to as asphaltum oil, liquid asphalt, black oil, residuum, etc,obtained as liquid or semi-liquid residues after the atmospheric orvacuum distillation of crude oils, are operable in this process althoughit may be desirable to blend such oils with lower boiling petroleumhydrocarbon fractions for economical operation. The petroleumhydrocarbon charge stock may boil substantially continuously betweenabout 400 F. and about 1200" F. or it may consist of any one, or anumber of petroleum hydrocarbon fractions, such as are set out above,which distill over within the 400-1200" F. range.

The catalysts of this invention are not deactivated to any appreciabledegree by the sulfur impurities which are frequently present in chargestocks such as are utilized in the present process. However, arelatively small amount of nitrogen present in the charge stock has anadverse effect on the process necessitating more severe operatingconditions and/or intermittent operation. In order to operatecontinuously over extended periods of time and under mild operatingconditions charge stocks which contain an excess of about 100 ppm.nitrogen should be treated to separate the excess nitrogen therefrom.This reduction in nitrogen content can be accomplished by conventionalmethods such as, for example, acid treatment, treatment with hydrogenunder pressure in the presence of catalysts comprising cobalt molybdate,cobalt tungsda-te, nickel sulfide, etc., or by any other suitable means.

Since the petroleum hydrocarbons which are hydrocracked according to theprocess of this invention boil over a considerably wide range, it may bereadily perceived that suitable reaction temperatures will lie within acorrespondingly wide range, the preferred temperature ranges dependingin each instance upon the particular petroleum hydrocarbon fractionutilized as a charge stock. For example, reaction temperatures of fromabout 400 F. to about 1000 F. are generally operable. However, where theparticular petroleum hydrocarbon fraction utilized boils within therange of from about 700 F. to about 900 F., it is preferred to operateat reaction temperatures in the more restricted range from about 500 F.to about 700 F.

Hydrogen is reacted with the cracked petroleum hydrocarbon at a pressureof from about 500 p.s.i. to about 3000 p.s.i., or preferably at fromabout 1200 p.s.i. to about 1800 p.s.i. The ratio of hydrogen to thepetroleum hydrocarbon charge stock is from about 5000 s.c.f. to about15,000 s.c.f. per barrel of charge stock although amounts of from about1000 s. c.f. to as much as 30,000 s.c.f. per barrel are operable. Theliquid hourly space velocity of the petroleum hydrocarbon charge stockcan be from about 0.1 to about depending on the particular charge ofemployed and the reaction temperatures necessitated thereby. A suitablecorrelation between space velocity and reaction temperature can bereadily determined by one skilled in the art in any particular instance.When utilizing the charge stock boiling in the range of from about 700F. to about 900 F., a liquid hourly space velocity of from about 1.0 toabout 3.0 is preferred.

A synthetic silica-alumina composite upon which a metal of Group VIII isdeposited is particularly adapted to the process of this invention.Several alternative procedures are available for the preparation of thesilicaalumina composite. In one method, a suitable mineral acid, such assulfuric acid, hydrochloric acid, or nitric acid, is added to an aqueoussolution of an alkali metal silicate, sodium silicate being preferredbecause of its low cost and ready avail-ability. In a second method theorder of addition is reversed, the water glass being added to the acid;this technique is preferred since formation of the silica sol alwaysoccurs under acid conditions and there is little danger of the solsolidifying prematurely as is the case in the former method when the pHof the system is being reduced from a high value to a low value. Whenusing sulfuric acid, concentrations thereof from about 10% to about 30%are satisfactory. The water glass solution may be prepared fromcommercial sodium silicates such as Philadelphia Quartz Company, brandsE, M, N, or S; the commercial water glass is first diluted with water toreduce the silica concentration thereof to from about 5% to about 15% byweight. The volumetric quantities and concentrations of the reactantsshould be adjusted to yield, upon mixing of acid and water glass, asilica sol containing from 20 to grams of silica per liter of sol, andat a pH of from about 3.5 to about 4.5. The commingling of acid andwater glass is preferably carried out relatively slowly, and withstirring, a mixing time of about 45 minutes being adequate therefor.

After the acid and Water glass have been commingled, the resultantsilica sol is allowed to age at a pH of from about 4 to about 4.8, andpreferably 4 to 4.5 or more advantageously 4 to 4.2 for at least 2.5hours. The sol will become a viscous hydrogel within a period of 5minutes to 2 hours, depending upon its composition, initial pH, extentof dilution, aging temperature and other factors. Due care should beexercised during this period to prevent the gel from solidifying, whichcan be accomplished :by stirring or agitating the gel and by addingquantities of water if necessary. Following the acid aging treatmentsufficient alkaline reagent, e.g. NH OH, is added to raise the pH of thegel to basic or near basic conditions, that is, to a pH of at least 6.5and preferably to a pH of from 7.0 to 7.5, or still more advantageouslyfrom about 7.0 to about 7.2, and the gel is further aged under suchbasic conditions for at least one hour.

Upon completion of the basic aging period, sufficient aluminum salt,e.g. aluminum sulfate, aluminum chloride, aluminum nitrate, etc. isadded to the silica gel, with mixing, to provide a final catalystcomposite, containing from about 1% to about 50%, and preferably fromabout 10% to about 30%, alumina. This may be conveniently accomplishedby the addition of a 20%30% aluminum sulfate solution. After thoroughlyimpregnating the aluminum salt into the silica gel, a basicprecipitating agent is then added to increase the sol pH to 8.08.5, atwhich point the aluminum hydrolyzes and homogeneous precipitation of asilica-alumina composite occurs. A suitable basic precipitant is a10%-15% ammonium hydroxide solution, although other basic mediums suchas potassium hydroxide, sodium hydroxide, ammonium carbonate, alkylamines, etc. may be employed when desired. At this stage, thesilica-alumina composite exists as a gel slurried in a mother liquor.The slurry contains a considerable quantity of soluble salts, e.g.sodium sulfate, and/or ammonium sulfate, as reaction products of thewater glass, acid, and base. It is essential that the silica-aluminacomposite be recovered substantially free of the salts prior toutilization as a catalyst and/or catalyst support. This is generallyaccomplished :by filtering the mother liquor from the gel and subjectingthe gel to repeated water-washings. Prior art methods generally teachthat water-washing may be accomplished in whole or in part before dryingof the gel or in whole or in part subsequent thereto, and attach noparticular significance to the order of washing and drying with respectto the intended use of the finished catalyst. However, it has now beendiscovered that a correlation does exist between the order of washingand drying of the composite and the intended use of the finishedcatalyst when the intended use is in hydrocracking of petroleumhydrocarbons. It has been found that separation of the salts in a mannerwhereby only a portion of the salts, say from about to about 90%, areremoved prior to drying at a temperature of from about 200 F. to about500 F. and removing substantially all of the remainder subsequent todrying, will yield a silicaalumina composite which, when composited withthe catialytically active materials hereinafter defined, will form asubstantially improved hydrocracking catalyst. For example, as willbecome apparent from the appended examples, when the silica-aluminaslurry is dried prior to removal of any of the salts therefrom aninferior hydrocracking catalyst results therefrom. Similar results areobtained where substantially all of the salts are removed prior todrying. However, where only a portion of the salts, say from about 10%to about 90%, are removed prior to drying at a temperature of from about200 F. to about 500 F., a considerably improved hydrocracking catalystis obtained.

Removal of a suitable portion of the salts can be accomplished simply bythe separation of the above mentioned mother liquor from thesilica-alumina dispersed therein by decantation, filtration or any otherconventional means. The silica-alumina can be re-slurried in water andfiltered a number of times to reduce the salt content thereof to anydesired level. It is preferred to remove from about 30% to about 60% ofthe soluble salts prior to drying of the silica-alumina composite.

The silica-alumina composite is preferably dried by spray drying methodswherein an aqueous slurry of silicaalumina gel is sprayed in an atomizedstate into an atmosphere of hot inert gases to effect a rapidevaporation of the moisture therefrom. The drying step is carried out ata temperature of from about 200 F. to about 500 F. The driedsilica-alumina is then subjected to multiple stage washing to separatethe balance of the soluble salts therefrom. It is desirable to includein the multiple stage washing, a washing step utilizing a dilute(0.0l%0.1%) ammonium salt solution, such as an aqueous ammonium chloridesolution, to effect the removal of alkali ion, such as sodium ion,followed by a water wash. The silica-alumina composite is then dried,and calcined at a temperature of from about 800 F. to about 1400 F.

The above described silica-alumina composite is impregnated with a metalof Group VIII of the Periodic Table which includes platinum, palladium,iridium, osmium, rhodium, ruthenium, nickel, iron and cobalt. In onepreferred embodiment of this invention palladium is utilized. In anotherpreferred embodiment nickel is employed.

Impregnation with the Group VIII metal can be accomplished by anysuitable or conventional methods. For example, the silica-alumina isimmersed in an aqueous solution of chloroplatinic acid, bromoplatinicacid, platinum chloride, palladium chloride, chloropalladic acid, etc.,or an aqueous solution of a salt of iron, nickel, cobalt, such as ferricchloride, ferric bromide, ferric fluoride, ferric nitrate, ferricsulfate, ferric formate, ferric acetate, etc., cobalt nitrate, cobaltfluoride, cobalt iodide, cobalt bromide, cobalt chloride, cobaltacetate, cobalt formate, etc., nickel chloride, nickel bromide, nickeliodide, nickel fluoride, nickel nitrate, nickel sulfate, nickel acetate,nickel formate, etc., such that the liquid is substantially taken up bythe silica-alumina, the concentration of the solution being such as toinsure a metal deposite of from about 0.1% to about 10% by weight of thefinal catalyst. The catalyst is then dried, usually at temperatures atfrom 6 about 200 to about 350 F., and calcined. When so desired, thecatalyst preparation may be completed by reduction with hydrogen orother methods known to the art, or it may be so reduced immediatelyprior to use.

The process of this invention can be carried out by conventional methodsand utilized standard equipment. For example, a system comprising amoving catalyst bed wherein the reactant flow may be concurrent orcountercurrent to the catalyst fiow can be utilized, or the catalyst maybe contained in a fixed bed reactor. In the fixed catalyst bed systemthe petroleum hydrocarbon and hydrogen reactants are charged to asuitable high pressure reactor equipped with heating means andcontaining therein a fixed catalyst bed comprising the catalyst of thisinvention. Said reactants can be commingled before entering the reactoror they can be charged thereto in individual and separate streams; alsothe reactants may be charged in an upflow or in a downflow manner. Thereactor efiluent is collected in a high pressure separator wherein thehydrocarbon products are separated and the excess hydrogen recovered forrecycle purposes and recycled by means of a recycle compressor.

The following examples are presented for the purpose of illustrating theprocess of the present invention and it is not intended to thereby limitthe generally broad scope of this invention.

EXAMPLE I A silica-alumina gel was prepared by first diluting ml. ofconcentrated sulfuric acid with 400 ml. of water. 1610 grams of waterglass was diluted with 3220 ml. of Water and added with stirring to thediluted sulfuric acid over a 30 minute period. The final pH was 3.3.After one hour of stirring, the sol became viscous and 3230 ml. of waterWas added thereto. 6000 ml. of water and 15 ml. of ammonium hydroxidewas then added to bring the pH of the sol to 7.0. The sol was stirred atthis pH value for one hour after which 1570 ml. of an aluminum sulfatesolution (sp. gr. 1.28) was added. The pH at this point was 3.2. 640 ml.of ammonium hydroxide and 640 ml. of water Was added to the sol bringingthe pH to 8.0. The gel was slurried for about 15 minutes. At this pointthe slurry was separated into three portions hereafter designated as A,B and C.

The portion of the above described slurry designated as A was spraydried Without further treatment. The spray dried material was thereafterslurried about five times in 2 liters of water and 20 ml. of 5% ammoniumchloride, and one more time in 2 liters of Water to remove substantiallyall of the soluble salts therefrom. The resultant silicaaluminacomposite was then dried at 300 F., made into /s" pills and calcined forthree hours at 1200 F. The resultant composite contained about 1.5 wt.percent sulfate.

A second portion of the above described slurry designated as B wasfiltered, thereby removing about /3 of the soluble salts, and theresidue was reslurried in water. This slurry of the filteredsilica-alumina gel was spray dried, and further treated as was Apreviously. The resultant composite contained about 1.3 wt. percentsulfate.

The third portion of the above described slurry designated as C wasfiltered and the residue reslurried in water and further filtered. Thisprocedure was repeated until the filtrate was substantially free ofsoluble salts. The salt-free silica-alumina gel was then reslurried inwater, spray dried, and further treated as was A previously. Theresultant composite contained about 0.6 wt. percent sulfate.

The A3" silica-alumina pills prepared as above described comprise about75% silica and about 25% alumina. All three batches, designated A, B andC were further impregnated with palladium such that the palladium waspresent to the extent of 0.4% of the final catalyst weight.

The above :described catalysts were evaluated as to hydrocrackingactivity by means of a relative activity test. The test comprisesprocessing a 340 white oil (286 API, boiling range 690-875 F.) and 3000s.c.f./bbl. recycle hydrogen over 100 cc. of a standard hydrocrackingcatalyst in a fixed bed, said catalyst comprising 0.4% palladium incommercial 25% A1 cracking catalyst. The white oil was processed overthe catalyst at a LHSV of l, 2 and 4. In each case the liquid productwas subjected to Engler distillation to determine the percent over at650 F. and the result was plotted against liquid hourly space velocity(LHSV). The standard" catalyst was arbitrarily assigned an activity of100. The results are tabulated below and illustrate the hydrocrackmgcapacity of the standard catalyst.

Table 1 Liquid Product:

LHSV 1 2 4 API gravity 54. 9 47. 9 39. 7 Engler dist.:

Percent at 180 F... 16. 5 8. 2 1. 3 Percent at 400 F-.. 62. 7 42.1 20. 1Percent at 650 F 85. 1 69. 9 43. 0 Carbon on Catalyst, wt.

percent 1 1 15 Gaseous Product, wt., porcen 1 Carbon on catalyst is theresult of a thirty hour test comprising test runs at 1, 2, and 4 LHSV.

The hydrocracking activity of the sample catalyst was then determined byprocessing the white oil over the sample catalyst at the aforesaidconditions, subjecting the resulting liquid products to Englerdistillation to determine the percent over at 650 F., and plotting theresult against LHSV. The relative activity of the sample catalyst wasthen determined as the ratio of the LHSV required to yield a liquidproduct 60% of which distills over at 650 F., to the LHSV required forthe same yield in the presence of the standard catalyst. The relativeactivity number is the fraction representing the aforesaid ratio,multiplied by the activity of the standard catalyst (100). The resultsof the relative activity tests of the catalysts A, B and C of Example Iare tabulated below:

even though the final sulfate content thereof is in considerable excessof catalyst C.

The data set out in the foregoing table is the result of a once-throughoperation. The product recovered from this once-through operationcontains a hydrocarbon fraction boiling in excess of the gasolineboiling range. This hydrocarbon fraction can be economically utilized asa high grade fuel oil or it can be recycled for increased gasolineyields as it is excellent charge stock for the hydrocracking process.

I claim as my invention:

1. A process for the preparation of a silica-alumina supported GroupVIII metal hydrocracking catalyst which comprises commingling an alkalimetal silicate solution with a sufficient quantity of a mineral acidsolution to form an acidic-salt-containing silica sol, first gelling andaging the resultant salt-containing sol under acid conditions, and thenadding an alkaline reagent and further aging the resultant gel underbasic conditions, commingling the resultant aged gel with an aluminumsalt solution, precipitating a silica-alumina composite therefrom by theaddition of a basic precipitant sufficient to raise the pH to at least8, water washing the freshly precipitated, undried silica-aluminacomposite sufiiciently to remove from about 10% to about 90% but not allof the water soluble salts therefrom, drying said water washedsilica-alumina composite at a temperature of from about 200 F. to about500 F, further water washing the resultant dried silica-aluminacomposite sufficiently to remove the remaining water soluble saltstherefrom, calcining the thus purified silica-alumina composite at atemperature of from about 800 F. to about 1400 F., and impregnating thecalcined silicaalumina composite with a Group VIII metal catalyticcomponent.

2. The process of claim 1 further characterized in that the pH of saidsilica sol during the acid aging thereof is maintained in the range offrom about 4 to about 4.5.

3. The process of claim 2 further characterized in that said alkalimetal silicate solution is added to said miner-a1 acid solution untilthe pH of the resultant silica sol is in the range of from about 3.5 toabout 4.5.

4. The process of claim 3 further characterized in that the pH of saidsilica gel during the basic aging thereof is maintained in the range offrom about 7.0 to about 7.5.

Table [1 Catalyst A B (3 Relative activity 27 147 49 Liquid Product:

LHSV API gravity Engler dist.:

Percent at 180 F Percent at 400 F Percent at 650 F Carbon on Catalyst,wt. percent- Gaseous Product, wt. percent" C1-C3 1 Carbon on catalyst isthe result of a thirty hour test comprising test runs at 1, 2, and 4LHSV.

It is apparent that hydrocracking of petroleum hydrocarbons according tothe process of this invention results in an excellent yield of productsfalling within the gasoline range with a minimum formation of coke and C-C hydrocarbons. The data further points out that ,waterwashing thefreshly precipitated silica-alumina gel sufficiently to remove only aportion of the soluble salts prior to drying of the silica-aluminacomposite as herein taught, results in a more active hydrocrackingcatalyst than is the case where the salts are substantially completelyremoved either before or after drying. Comparison of the resultsobtained from the testing of catalyst B and C show that catalyst B,prepared according to the method of this in- 5. A process for thepreparation of a silica-alumina supported Group VIII metal hydrocrackingcatalyst which comprises commingling an alkali metal silicate solutionwith a sufiicient quantity of a mineral acid solution to form asalt-containing silica sol having a pH of from about 3.5 to about 4.5,gelling and aging the resultant salt-containing sol at a pH of fromabout 4 to about 4.5, and then adding an alkaline reagent and furtheraging the resultant gel at a pH of from about 7 to about 7.5,commingling the resultant aged gel with an aluminum salt solution,precipitating a silica-alumina composite therefrom by adding asufiicient amount of a basic precipitant to raise the pH to about 8,water washing said silica-alumina composite,

vention, is by far the more active hydrocracking catalyst prior todrying thereof, sufiiciently to remove from about 10% to about 90% butnot all of the water soluble salts therefrom, forming an aqueous slurryof said Water Washed silica-alumina composite and spraying the slurry inan atomized state into an atmosphere of hot inert gases maintained at atemperature of from about 200 F. to about 500 F. to effect a rapidevaporation of the moisture therefrom, fiurther Water Washing theresultant spray dried silica-alumina composite sufficiently to removethe remaining Water soluble salts therefrom, calcining the rth'uspurified silica alumina composite at a temperature of from about 800 F.to about 1400 F., and impregnating the calcined silica-alumina compositewith a Group VIII metal catalytic component.

6. The process of claim 1 fiuuther characterized in that from about 30%to about 60% o f the water soluble salts are removed from said freshlyprecipitated, undried silicaalumina composite by the first-mentionedwater washing step.

References Cited by the Examiner OSCAR R. VERTIZ, Primary Examiner.

DELBERT E. GANTZ, BENJAMIN HENKIN,

Examiners.

A. RIMENS, E. J. MEROS, Assistant Examiners.

1. A PROCESS FOR THE PREPARATION OF A SILICA-ALUMINA SUPPORTED GROUPVIII METAL HYDROCRACKING CATALYST WHICH COMPRISES COMMINGLING AN ALKALIMETAL SILICATE SOLUTION WITH A SUFFICIENT QUANTITY OF A MINERAL ACIDSOLUTION TO FORM AN ACIDIC-SALT-CONTAINING SILICA SOL, FIRST GELLING ANDAGING THE RESULTANT SALT-CONTAINING SILICA SOL, FIRST GELLING AND AGINGTHEN ADDING AN ALALINE REAGENT AND FURTHER AGING THE RESULTANT GEL UNDERBASIS CONDITIONS, COMMINGLING THE RESULTANT AGED GEL WITH AN ALUMINUMSALT SOLUTION, PRECIPITATING A SOLICA-ALUMINA COMPOSITE THEREFROM BY THEADDITION OF A BASIS PRECIPITANT SUFFICIENT TO RAISE THE PH TO AT LEAST8, WATER WASHING THE FRESHLY PRECIPITATED, UNDRIED SILICA-ALUMINACOMPOSITE SUFFICIENTLY TO REMOVE FROM ABOUT 10% TO ABOUT 90% BUT NOT ALLOF THE WATER SOLUBLE SALTS THEREFROM, DRYING SAID WATER WASHEDSILICA-ALUMINA COMPOSITE AT A TEMPERATURE OF FROM ABOUT 2000F. TO ABOUT500*F., FURTHER WATER WASHING THE RESULTANT DRIED SILICA-ALUMINACOMPOSITE SUFFICIENTLY TO REMOVE THE REMAINING WATER SOLUBLE SALTSTHEREFROM, CALCINING THE THUS PURIFIED SILICA-ALUMINA COMPOSITE AT ATEMPERATURE OF FROM ABOUT 800*F. TO ABOUT 1400*F., AND IMPREGNATING THECALCINED SILICAALUMINA COMPOSITE WITH A GROUP VIII METAL CATALYTICCOMPONENT.